BackgroundThe high burden of perinatal mental health (PMH) conditions has spurred international efforts to integrate PMH services into primary healthcare (PHC). Despite the existence of evidence-based PMH interventions endorsed by the World Health Organization (WHO), there is lack of guidance frameworks for the effective and sustainable integration of these interventions into PHC systems to make them fair and responsive to women and infant needs, particularly in low- and middle-income countries (LMICs). ObjectiveWe propose the "Implementation Framework for Integration into the Primary Healthcare System" (IF-IPHS) – a systematic approach to guide integration of PMH interventions into PHC settings. Approach and framework componentsOur approach is based on contemporary, empirically-derived frameworks and WHO guidelines on PMH, emphasising the significance of implementation science and health system thinking. The implementation framework for integration into the PHC system consists of two iterative phases: (I) Adaptation: involves modifying and pilot-testing of established PMH interventions to meet target population needs, guided by human-centred design. (II) Adoption: focuses on development of policies and resource allocation mechanisms through mobilization and stakeholder engagement for sustained integration of PMH intervention across all healthcare system components. Broader applicabilityThe IF-IPHS is designed to assist and empower health system stakeholders (e.g. policymakers, practitioners, researchers, funders) in LMICs. It offers practical guidance for systematically integrating effective PMH interventions into PHC systems through context-specific adaption process and adoption strategies, taking a holistic approach beyond mere clinical and programmatic considerations. It can also serve as a flexible roadmap for integrating various health interventions beyond PMH within PHC systems.